A two-thousand-year-old technique
Gilding with pure gold leaf is a decorative process that consists in covering an object with a very fine layer of gold. Egyptian were the first to use gold for decoring and to practice the millwork, two thousands years ago. Many gilding processes are available: Bruno Barbon uses water gilding, a technique that gives incomparable transparency and brilliance.
Gold leaf. Gold is a precious metal, reddish-yellow in colour, extremely shiny when polished, soft and ductile. It is unalterable by air and is almost never used in its pure form because it is two soft, therefore it is alloyed with silver or copper, which make it harder. The gold used for restoration of gilding is in the form of extremely fine leaves of a thickness of between 0.00001 mm and 0.00008 mm, which are gathered in booklets. The cost of a booklet varies depending on the carats of the gold, in other words, based on its purity.
The phases of the process
Priming. The first phase in the gilding process is consists in making the surface to be gilded even and is known as priming. First the object is covered in glue, which is slightly coloured with powdered pigment (umber). The next step is the apply stucco and gesso. The gesso is combined with rabbit-skin glue and painted on in order to prepare a smooth and even surface.
Applying bole. Once the gesso has dried, the surface is sanded down so that the details of the carving emerge again, partly softened by the applications of gesso. Having eliminating all dust residue, the bole is applied. This is a solution made up of a special powder extracted from a quarry in Armenia mixed with fish or rabbit-skin glue.
Gold leaf application. Once the bole has dried, the actual gilding begins. First the water size is prepared – this is a solution made up of water and fish glue – and an area of the surface as large as the leaf to be applied is moistened. The leaf is cut to size with a special knife and applied delicately to the moistened area using a flat brush. Once the gilding is complete, the area is with blotted with padding in order to perfect adhesion of the leaf.
Burnishing. Having removed the excess of gold leaf, it is burnished to bestow the gold leaf with the shine typical of metal. In order to do this, an agate stone is used, applied directly to the leaf, or special tools called burnishers are used. The job is completed with the application of a layer of protective varnish.